FORM 6-K SECURITIES AND EXCHANGE COMMISSION Washington D.C. 20549 Report of Foreign Issuer Pursuant to Rule 13a-16 or 15d-16 of the Securities Exchange Act of 1934 For period ending March 26, 2008 GlaxoSmithKline plc (Name of registrant) 980 Great West Road, Brentford, Middlesex, TW8 9GS (Address of principal executive offices) Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F Form 20-F x Form 40-F -- Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934. Yes No x -- Notification of Transactions of Directors, Persons Discharging Managerial Responsibility or Connected Persons Following a re-valuation of the cash element of the notional investment held within the US Retirement Savings Plan ("The Plan"), which is notionally held in GSK Ordinary share ADRs, the Administrators of the Plan notified GlaxoSmithKline plc and the under-mentioned person on 26 March 2008 of an increase in the notional allocation of Ordinary share ADRs on 24 March 2008 at a price of $42.14 per ADR:- Dr R G Greig 6 This notification relates to a transaction notified in accordance with Disclosure and Transparency Rule 3.1.4R(1)(a). S M Bicknell Company Secretary 26 March 2008 SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorised. GlaxoSmithKline plc (Registrant) Date: March 26, 2008 By: VICTORIA WHYTE ------------------ Victoria Whyte Authorised Signatory for and on behalf of GlaxoSmithKline plc